Rapid RegEx Developer
Like every well-adjusted programmer I adore regular expressions but, since I use them only occasionally, I can never remember all the required details and subtlety. It often takes me several iterations to get the regex to do what I want it to. That's why I wrote this program.
You put your source text in the middle box, bang out some regex in the top box and any and all matches (and groups) show up in the bottom box. Every keyup event is linked to the regex processor so you can see exactly how your expression evaluates with each tweak to the pattern.
The Help menu has a few links to online regex references in case you can't remember the exact syntax for group callbacks. If you're looking down the barrel of some tricky regular expression development I would recommend you download this tool and give it a try. Once you realize how easy it is you'll be building entire web servers out of nothing but complex regexes.
Requires the Microsoft .NET Framework (v2.0)
2.0.1 Fixed problem reading/writing registry keys under Windows 7 (and probably also Vista).